Re: Piranha's Call-Off-Load feature. What format is used for the too and from phone numbers? Canonical international? With or without dialing codes? Has anyone used this feature?

I would use 0039xxxx

So, *110*0012345551212*00442034614444#<SEND>
would connect a call from a hypothetical number in the US to the Bank of England's switchboard in UK?

Yes, that should work.

Does the Piranha Mobile SIM work in an iPhone 3GS?

I have an old, unlocked iPhone 3GS. I've tested it with a T-Mobile SIM and it works fine. When I insert the Piranha SIM, it starts off with "Searching" and ends up on "No Service." Putting the phone in and out of Airplane Mode produces "Invalid SIM".

The SIM works perfectly in my Moto G.

I do not see why not, since you said it's unlocked. Mine works in my unlocked AT&T Iphone 4.

It appears that it has to do with the default crippled mode of AT&T phones. When I insert my T-Mobile PAYG SIM, after a few minutes it updates the settings and give me the manual carrier selection menu and T-Mobile STK. With the Piranha SIM it does not do this. The phone has iOS 6.1.6, which is up-to-date for this phone. I'm also getting advice from Piranha Mobile but so far, no joy.

I wanted to use the old iPhone 3G because it has all the needed bands and is expendable.

Today I had to remove from my dual sim phone my Piranha cause even if it seemed that everything was ok (good signal on the phone) the sim was not registered on network and if called said "sim out of coverage" .
I am very disappointed, all problems I had with the initial setup seemed solved but as of today that's not the case.
Anyone else with the same issue?

have you tried another handset, i had issues with my dual SIM handset, SIM was fine when i changed back to the single SIM handset. What make and model are you using??

Thanks for replying. I am using a Oneplus 3T, that's strange because this sim after a bit of problems at the beginning when registering, was working ok. Anyway there's always a big delay in registering on the network. I contacted the customer care and they said it could be Tim (the Italian carrier) could have experienced some issues.